1. Field of the Invention
The present invention relates to a medical electrode for intracorporeal stimulation of body tissue, particularly for intracardial stimulation of heart tissue, and to a device for implanting such an electrode.
2. Description of the Prior Art
Electrodes for medical purposes are generally known which include an electrode cable containing at least one elongated flexible conductor terminating in an electrode head at a distal end of the cable (as used herein, "distal" means distal from a yet-to-be-connected source of therapeutic electrical energy, and "proximate" means the end of the cable closer to that source). The electrode cable is provided with a layer of insulation.
It is of great importance for the electrode cable to be sufficiently pliant so that it is able, during advancement, for example, to heart of a patient via a vein, to follow the course of the vein without damaging the venous wall. The electrode cable is conventionally introduced using a stylet which is inserted into a channel in the cable. The stylet consists of a material having a sufficient stiffness required to advance the cable through the vein. At difficult passages, for example, where the cable must bend sharply, the stylet is often slightly retracted, so that the distal end of the electrode cable displays maximum pliancy. After such a passage has been negotiated, the stylet is again advanced to the distal end of the electrode cable in order to push the end into, for example, the atrium or into the ventricle, until the electrode head comes into contact with the heart wall for stimulation of the heart. Advancing the electrode cable in a vein with the aid of a stylet, which temporarily makes the electrode cable relatively stiff, is therefore not a simple procedure for the operator. Medical electrodes of the above-described type, wherein the cable is advanced through a vein with the aid of a stylet, are described in U.S. Pat. Nos. 4,136,703, 4,402,328 and 4,677,990.